The question of lifetime of digital recording is a murky one.
Some manufacturers (e.g. Kodak) now claim 200 years for a
properly stored (shielded cold vault) CD-R. That would be
comparable to books.
But in practice technology changes govern lifetime. When did you last
see a computer with 5.25" floppies or 1/2" magnetic tape? That means
media transfers are needed every 10-20 years to keep it accessible.
A book printed in 1800 on good quality paper is still readable.